Wind turbine provided with a controller for adjusting active annular plane area and the operating method thereof

ABSTRACT

A wind turbine which varies an active annular plane area by composing such that blades are attached to a cylindrical rotor movable in the radial direction of the rotor, the blades being reciprocated in the radial direction by means of a blade shifting mechanism connected to the root of each blade, or the blade itself is divided so that the outer one of the divided blade is movable in the radial direction. With the construction, the wind turbine can be operated with a maximum output within the range of evading fatigue failure of the blades and rotor by adjusting the active annular plane area in accordance with wind speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is a wind turbine generator and relates to a windturbine having a plurality of blades attached to a rotor, the rotatingforce generated by allowing wind force to act on the blades beingtransmitted to the output shaft of the rotor, wherein a controller of anactive annular plane area is provided for making it possible to changethe active annular plane area of the wind turbine by reciprocating eachof the blades in a radial direction or by slanting the rotor and theoperating method thereof.

2. Description of the Related Art

A wind turbine power plant having high capacity of generating electricpower by installing a plurality of wind turbine electric power generatorunits, each of which utilizes the rotating force generated by applyingwind force to a plurality of blades attached to a rotor to drive agenerator via the wind turbine shaft, is constructed at high elevationsuch as the top of a hill or mountain or at a place where high windvelocity can be received, such as above the sea.

The wind turbine apparatus used for driving an electric generator orother purposes is constructed, as shown in FIG. 1 of patent document 1(Japanese Patent Application Publication No. 5-60053) and In FIG. 1 ofpatent document 2 (Japanese Patent Application Publication No.5-60053)), such that a plurality of blades are attached to the peripheryof a rotor head and the rotating force generated by wind force istransmitted to the turbine shaft via the rotor head. Desired ordetermined electric power generation is maintained by changing the pitchangle of the blades attached to the rotor in accordance with the windspeed and required electric power while controlling to adjust the bladepitch angle to the angle optimal for the wind speed blowing when theapparatus is in operation.

In the wind turbine of FIG. 1 of patent document 3 (Japanese PatentApplication Publication No. 2001-99045), blades are attached to a rotorhead such that the blades are supported for rotation via bearings fixedto the rotor head, bevel gear mechanism is provided inside the rotorhead to be driven by a servomotor. The pitch angle of the blades ischangeable by rotating the blades relative to the rotor head by theservomotor via the bevel gear mechanism.

The output power of the wind turbine generated by the action of wind isabout proportional to active annular plane area, i.e., the area of theannular plane formed between the circumscribed circle of the blade tipsand the inscribed circle of the blade roots.S=π(L ² −I ²)  (1)where S is active annular plane area, L is radius of the circumscribedcircle, and I is radius of the inscribed circle.

In order to increase the output power of a wind turbine, it is requiredthat radius L is increased or the difference between L and I, that meansthe length of the blade is increased.

The power P_(W) that the wind passing through active annular plane areaS has, isP _(W) =k·S·V ³  (2)where V is wind speed, and k is air density divided by 2.

As wind speed depends on weather conditions at the location of the windturbine, the output of the wind turbine, that is the electric powergenerated in the case of wind turbine electric generator, can beincreased by increasing the active annular plane area.

However, in the case where the active annular plane area is increasedfor increasing output power, the rotating components such as the bladesand rotor are more likely to be broken by fatigue failure resulting frombeing subjected to repeated excessively fast wind speed V of a gust ofwind, etc., which sometimes occurs according to weather conditions,although the output is increased.

With the prior art disclosed in patent documents 1 and 2, because theblades are fixed to the rotor head of a somewhat larger diameter thanthe rotor shaft, it is difficult to design a longer blade, that is, toincrease radius L, so that there is a limit for increasing the output ofa wind turbine. Further, when blade length is increased to the maximumto increase active annular plane area for increasing the output of thewind turbine, the rotating components such as the blades and rotor tendto be broken by fatigue failure due to repeated occurrence of a gust ofwind, etc., of excessively increased speed.

The wind turbine of patent document 3 has a means for changing bladepitch angle by rotating the blades relative to the rotor head, however,the active annular plane area is not variable but constant, and thereremains also the problem that the rotating components such as the bladesand rotor tend to be broken by fatigue failure resulting from beingsubjected to repeated excessively increased speed of a gust of wind,etc.

SUMMARY OF THE INVENTION

The first objective of the present invention is to provide a windturbine with which an active annular plane area of the blades isvariable corresponding to wind speed by changing the radial positioningof the blades and the output of the wind turbine can be maintained at amaximum while avoiding the occurrence of fatigue failure.

The second objective of the present invention is to provide a windturbine with which an active annular plane area of the blades isvariable corresponding to wind speed by changing the effective length ofblades and the output of the wind turbine can be maintained at a maximumwhile avoiding the occurrence of fatigue failure.

The third objective of the present invention is to provide a windturbine with which an active annular plane area of the blades isvariable corresponding to operating conditions, such as wind speed,etc., and at the same time corresponding to the stress of the rotatingcomponents of the wind turbine by changing the effective length ofblades and the output of the wind turbine can be maintained at a maximumwhile avoiding the occurrence of fatigue failure.

The fourth objective of the present invention is to provide a windturbine which is provided with an active annular plane area adjustingdevice which makes it possible to change an active annular plane areacorresponding to the speed of the wind in the direction of the axis ofrotation of the rotor head of the wind turbine by connecting the bladesto the rotor head by means of rotatable connecting elbows and the outputof the wind turbine can be maintained at a maximum while avoiding theoccurrence of fatigue failure.

The fifth objective of the present invention is to provide a windturbine with which an active annular plane area of the blades isvariable corresponding to wind speed by tilting the blades toward theaxis of rotation and the output of the wind turbine can be maintained ata maximum while avoiding the occurrence of fatigue failure.

To attain the objectives, the wind turbine is composed as follows.

The first means of the present invention is a wind turbine with anactive annular plane area control mechanism comprising a plurality ofblades attached to a rotor for transmitting the wind force acting on theblades to the output shaft of the wind turbine connected to the rotor,wherein said rotor is formed in a cylindrical shape, said blades areattached to said rotor movable in a radial direction of the rotor, ablade shifting mechanism is connected to the roots of said blades forreciprocating said blades in the radial direction, and an active annularplane area is changeable by moving said blades in the radial directionthrough said blade shifting mechanism.

The rotor of said wind turbine has preferably radial fit holes locatedat an equal spacing in the circumferential direction, said blades arereceived in said radial fit holes for reciprocation, and said bladeshifting mechanism is provided in the hollow of said rotor.

Said wind turbine is preferably provided with a wind speed detector fordetecting the speed of the wind acting on said blades and a controldevice which receives the detected wind speed from said wind speeddetector, calculates a desired active annular plane area and the radialposition corresponding to said active annular plane area on the basis ofsaid detected wind speed, and outputs the result to said blade shiftingmechanism.

Said blade shifting mechanism preferably comprises a plurality of screwbars received for rotation in radial holes provided in the cylindricalwall of said rotor, sleeves each of which is engaged with each of thescrew bars, links each of which connects each of said links and saidblades, pinions each of which is fixed to each of said screw bars at theinner side part thereof, and a driving gear meshing with said pinionsand driven by a driving device such as a motor; and said blades arereciprocated in the radial direction through the expansion orcontraction of said links resulting from the shifting of said sleeves bythe rotation of said screw bars when said driving gear is rotated bysaid driving device.

Further, said blade shifting mechanism preferably comprises a supportingelement located in the center part of said rotor; pairs of links capableof being expanded or contracted, each pair connecting the root of eachblade to said supporting element, screw bars each connecting one side ofeach of said pairs of links, and driving devices such as motors forrotating said screw bars; and the radial position of said blades ischangeable by expanding or contracting said pairs of links throughrotating said screw bars by said driving devices.

Yet further, said blade shifting mechanism preferably comprises tworings, an outer ring and an inner ring, provided concentrically with thecenter axis of said rotor rotatable in the direction contrary to eachother, pairs of links capable of being expanded or contracted, each pairconnecting the root of each blade to the outer ring with one of the pairand to the inner ring with the other of the pair, a driving device forrotating said two rings in the direction contrary to each other, and asupporting element located in the center part of said rotor and supportsone of said rings; and said blades can be reciprocated in the radialdirection by expanding or contracting said pairs of links throughrotating said rings in the direction contrary to each other.

Still further, said blade shifting mechanism preferably comprises aslider received in a slider receiver fixed to the rotor 2 for sliding inthe radial direction of the rotor, the slider having a screw thread holedirected in the radial direction, links each of which has a curvedconvex surface at an end thereof to be engaged in a convex of curvedsurface formed in said slider receiver to be supported for swinging, theother end having an elongated hole through which the link is connectedto the lower end part of the blade via a pin fixed to said lower part, ascrew bar engaged with said screw thread hole of said slider, and adriving device such as a motor for rotating said screw bar; and theblades can be reciprocated in the radial direction via said elongatedhole and said pin engaging in said hole by moving said slider in theradial direction in said slider receiver through rotating said screw barby the rotation of said driving device.

The second means of the present invention is an operating method of thewind turbine with an active annular plane area control mechanismcomprising a plurality of blades attached to a rotor for transmittingthe wind force acting on the blades to the output shaft of the windturbine connected to the rotor, wherein the speed of the wind acting onthe wind turbine is detected, and the blades attached to the rotorcapable of being moved in the radial direction of the rotor are moved inradial outward directions to increase an active annular plane area asthe detected wind speed decreases and the blades are moved in radialinward directions to decrease the active annular plane area as thedetected wind speed increases.

The third means of the present invention is a wind turbine with anactive annular plane area control mechanism of a darrieus type windturbine which has supporting elements provided along a vertical windturbine shaft and a stage or a plurality stages of a plurality of setsof blades, each of which is supported by said supporting elements atboth ends thereof and located along said vertical wind turbine shaft,said wind turbine shaft being rotated by the aerodynamic lift effectedby the wind acting on said blades, wherein said supporting elements arecapable of being shifted in the radial direction perpendicular to saidwind turbine shaft, a blade shifting mechanism is provided for changingthe radial position of said set of blades by shifting said supportingelements in the radial direction, by which the radius of rotation ofsaid blades can be changed.

Said wind turbine of the third means is preferably provided with a windspeed detector for detecting the speed of the wind acting on said windturbine and a control device which calculates the desired active annularplane area and the shift amount to realize said desired active annularplane area and allows the blades to be shifted in radial outwarddirections by shifting said supporting elements through said bladeshifting mechanism in order to increase the active annular plane area assaid detected wind speed decreases, allows the blades to be shifted inradial inward directions in order to decrease the active annular planearea as said detected wind speed increases.

Said blade shifting mechanism in the third means preferably comprisesscrew bars erected upright parallel to said vertical wind turbine shaft,each screw bar having right-hand and left-hand screw thread parts cut byturns along the bar, one or a plurality of pairs of shifting elements,one of the pair being engaged with the right-hand or left-hand threadsof the two screw bars and the other being engaged on the contrary withthe left-hand or right-hand threads of the two screw bars so that thepair of the shifting elements move in the direction contrary to eachother by the rotation of said screw bars in the same direction, pairs oflinks each for connecting each supporting element to each of the pair ofshifting elements, and a driving device for rotating said screw bars;and the blades can be shifted in the radial direction by shifting saidsupporting elements in the radial direction through allowing the pair ofshifting elements to move in the direction contrary to each other byrotating said screw bars in the same direction by said driving device,said supporting elements being shifted in the radial direction by meansof said pair of links connecting itself to the pair of shiftingelements.

It is preferable in the third means that a driving device is connectedto an end side of one of said screw bars and said shifting elementsengaging with said screw bars are moved simultaneously.

The fourth means of the present invention is an operating method of thewind turbine with an active annular plane area control mechanism of adarrieus type wind turbine which has supporting elements provided alonga vertical wind turbine shaft and a stage or a plurality stages of aplurality of sets of blades each of which is supported by saidsupporting elements at both ends thereof and located along said verticalwind turbine shaft, said wind turbine shaft being rotated by theaerodynamic lift effected by the wind acting on said blades, wherein thewind turbine is constructed so that the radial position of the blades ischangeable by shifting the supporting elements in the radial directionperpendicular to the vertical turbine shaft, the speed of the windacting on the blades is detected, and the blades are moved in radialoutward directions by means of said supporting elements to increase theactive annular plane area as the detected wind speed decreases and theblades are moved in radial inward directions to decrease the activeannular plane area as the detected wind speed increases.

According to the first to fourth means, wind speed is detected by thewind speed detector and inputted to the controller. In the controller,relations between wind turbine output P, wind speed V, and activeannular plane area S are set beforehand, and a relation between thelimit wind speed with which fatigue failure occurs in the rotatingcomponents such as the blades and rotor and active annular plane area.The controller calculates an optimal active annular plane areacorresponding to the detected wind speed when the detected wind speed isinputted, and the result is outputted to the driving device of the bladeshifting mechanism.

Each blade is moved in the radial direction through the blade shiftingmechanism guided by radial holes provided in the cylindrical wall of therotor or in the darrieus type wind turbine the radial position of eachblade can be changed by moving the supporting elements supporting eachblade in the radial direction and the blades are kept in the positionwith which the active annular plane area is equal to said calculatedoptimal active annular plane area.

By this, it is possible that the blades are shifted in radial outwarddirections by shifting said supporting elements through said bladeshifting mechanism in order to increase the active annular plane area assaid detected wind speed decreases, and they are shifted in radialinward directions in order to decrease the active annular plane area assaid detected wind speed increases. Therefore, the wind turbine can beoperated with the radial position of the blades, with which the outputas high as possible is obtainable while evading the occurrence offatigue failure of the rotating components such as the blades and rotorunder the present wind speed.

Accordingly, by the means mentioned above, the wind turbine can beoperated while always automatically controlling blade length so that theoccurrence of fatigue failure of the rotating components, such as theblades and rotor, is reduced, and at the same time the wind turbine isoperated with the optimal active annular plane area which ensures themaximum output of the wind turbine in the range capable of evading thefatigue failure. Accordingly, the operation of the wind turbine ispossible with the optimal maximum output with elongated fatigue life ofthe rotating elements such as the blades and rotor.

The fifth means of the present invention is a wind turbine with anactive annular plane area control mechanism comprising a plurality ofblades attached to a rotor for transmitting the wind force acting on theblades to the output shaft of the wind turbine connected to the rotor,wherein each of said blades is configured so that blade length can bechanged in the total length of the blade or in a certain length from themiddle up to the tip of the blade, a blade length adjusting mechanism isprovided for adjusting the blade length of each of the blades, and theactive annular plane area is changeable by changing the radial positionof the blades relative to the rotor by said blade length adjustingmechanism.

Each of said blades is preferably formed in a bellows shape expandableand contractible in the radial direction of the rotor, a plurality ofair chambers to which air is supplied or from which air is exhaustedbeing formed inside said bellows-shaped blade continuously in thedirection of blade length, and said blade length adjusting mechanism iscomposed of an air supply device for producing pressurized air and anair tube for supplying the pressurized air to each of said air chambers,the tube connecting said air supply device to each air chamber and beingmovable in the blade length direction as said bellows-shaped bladeexpands or contracts.

It is preferable in the fifth means that there are provided air valvesattached to said air tube for opening or closing outlets of the air intoeach of said air chambers and an air control device for controlling theopening and closing of said air valves and the operation of said airsupply device.

It is also preferable that there are provided a flexible string, such aswire connected to the top of the blade, and a flexible string drivingdevice for expanding or contracting the blade by drawing out or in theflexible string in the blade length direction to change the blade tipdiameter.

Further, it is preferable that each of said blades is divided into avariable length blade part and a blade body fixed to the rotor andconnecting to the root of said variable length blade part, said variablelength blade part is supported by said blade body capable of beingtilted around the supporting shaft of the variable length blade part,and said blade length adjusting mechanism is composed as a blade tiltingmechanism for tilting said variable length blade part around saidsupporting shaft by a driving device by means of a link mechanism.

Yet further, it is preferable that each of said blades is divided into avariable length blade part and a blade body fixed to the rotor andconnecting to the root of said variable length blade part, said variablelength blade part is received in the guide hole of said blade bodycapable of being moved in the direction of blade length, and said bladelength adjusting mechanism is composed as a blade reciprocating devicefor reciprocating the variable length blade part guided along said guidehole by a reversible driving device, such as a reversible motor, inorder to change the blade tip diameter.

Still further, each of said variable length blade parts has preferably arack fixed to the lower end thereof, and said blade reciprocating deviceis composed such that a pinion which meshes with said rack is fixed tothe output shaft of said reversible driving device to convert therotating motion of the reversible driving device to the reciprocatingmotion of the variable length blade part.

Yet still further, each of said variable length blade parts haspreferably a shaft with female screw thread fixed to the lower endthereof, and said blade reciprocating device is composed such that ascrew bar which engages in the female screw thread of said shaft isfixed to the output shaft of said reversible driving device to convertthe rotating motion of the reversible driving device to thereciprocating motion of the variable length blade part.

Further in the fifth means, each of said blades is divided into avariable length blade part and a blade body fixed to the rotor andconnecting to the root of said variable length blade part, said variablelength blade part is composed of a front core made of hard material suchas a metal pipe extended downward in the direction of blade length toform an actuating shaft part, a rear core made of wire of soft material,and a blade shell made of flexible material defining a blade profilebetween said front core and rear core, said actuating shaft part of thefront core is received for sliding in the direction of blade length in abearing hole provided in the blade body, and said blade reciprocatingdevice is composed as a blade reciprocating device for reciprocatingsaid variable length blade part through reciprocating said actuatingshaft part of the front core by means of a reversible driving devicesuch as a reversible motor.

According to the fifth means, an active annular plane area can beadjusted to an optimal area corresponding to wind speed even during theoperation of the wind turbine by varying the tip diameter of blades bychanging the effective blade length through shifting the blades in theradial direction of the rotor by means of the blade length adjustingmechanism, or by extending or contracting the blade itself in the bladelength direction.

By this, it is possible to operate the wind turbine so that an output ashigh as possible is obtained while evading the occurrence of fatiguefailure of the rotating components, such as the blades and rotor, underthe present wind speed by adjusting the effective length of each of theblade itself so that the blade tip diameter is increased by increasingthe effective blade length to increase active annular plane area as windspeed decreases, on the other hand the blade tip diameter is decreasedby decreasing the effective length to decrease active annular plane areaas wind speed increases.

Therefore, by the fifth means, the wind turbine can be operated whilealways automatically controlling blade length so that the occurrence offatigue failure of the rotating components such as the blades and rotor,and at the same time the wind turbine is operated with the optimalactive annular plane area which insures a maximum of the wind turbineoutput while avoiding fatigue failure.

Accordingly, the operation of wind turbine is possible with an optimalmaximum output with elongated fatigue life of the rotating elements suchas the blades and rotor.

Further, the blade length varying mechanism is constructed light inweight and can be provided inside the blade, so an active annular planearea is variable without accompanying the increase in the weight ofblade.

Further, according to the fifth means, active annular plane area can bechanged by changing the effective blade length by supplying orexhausting air to or from each of the independent air chamber formedcontinuously in the direction of the length the blade formed in abellows shape by opening or closing air valves through an air controldevice.

The blade tip diameter can be varied by extending or contracting saidblade through drawing out or in the flexible string such as wireconnected to the top of the blade by the flexible string driving device.

According to the fifth means, the projected area of the surface ofrevolution of the blade in the direction of the axis of rotation of therotor, i.e., active annular plane area is changeable by changing thetilt angle of each of the variable blade length parts through swingingeach variable blade length part which is supported at the root partthereof for rotation by the supporting shaft fixed to the blade body viathe link mechanism.

Further, according to the fifth means, an active annular plane area ischangeable by changing the blade tip diameter by reciprocating eachvariable length blade part fit for sliding in the guide hole of eachblade body via a rotation-reciprocation converting mechanism such aspinion-rack mechanism or screw bar-nut mechanism through the rotation ofthe reversible driving device such as a reversible motor.

Further, according to the fifth means, the active blade tip diameter ischangeable by reciprocating each variable length blade part by slidingthe actuating shaft which is the extended part of the front core of thevariable length blade part and fit for sliding in the guide hole of eachblade body via a rotation-reciprocation converting mechanism, such aspinion-rack mechanism, through the rotation of the reversible drivingdevice, such as a reversible motor.

Further, according to the present invention, each of the variable lengthblade parts composed of a front core made of wire, a rear core made ofsoft wire, and a blade shell made of flexible material defining bladeprofile between the front core and rear core, so that the variablelength blade part is made to be light in weight, and in addition tothat, as the blade shell is made of flexible material, the variablelength blade part can be folded, which results in ease oftransportation.

The sixth means of the present invention is a wind turbine with anactive annular plane area control mechanism comprising a plurality ofblades attached to a rotor for transmitting the wind force acting on theblades to the output shaft of the wind turbine connected to the rotor,wherein each of said blades is divided into a variable length blade partand a blade body fixed to the rotor and connecting to the root of saidvariable length blade part, and there are provided operating conditionsdetectors for detecting the operating conditions of the wind turbine, ablade length controller for comparing each of the detected signals ofthe operating conditions inputted from said operating conditionsdetectors with each of the predetermined permissible values of operatingconditions and calculating the amounts of active annular plane area andblade length to be adjusted for optimal operation based on the result ofcomparisons, and a blade length adjusting mechanism for changing bladelength based on the calculated blade length inputted from said bladelength controller.

It is preferable that said operating condition detectors include atleast one among a wind speed detector for detecting the speed of thewind acting on the wind turbine, a rotation speed detector for detectingthe rotation speed of a rotating component of the wind turbine includingthe rotor, and a load detector for detecting the load of the windturbine, and said blade length controller compares the signal ofdetected wind speed from said wind speed detector with a predeterminedpermissible value of wind speed, or compares the signal of detectedrotation speed from said rotation speed detector with a predeterminedpermissible value of rotation speed, or compares the signal of detectedload from said load detector with a predetermined permissible value ofload, calculates the amounts of active annular plane area and bladelength to be adjusted for optimal operation concerning at least oneamong wind speed, rotation speed, and load, and outputs the result tosaid blade length adjusting mechanism.

It is also preferable that a blade stress detector is provided fordetecting the stress occurred in the blade, and said blade lengthcontroller is composed so that the amounts of active annular plane areaand blade length to be adjusted for optimal operation are calculatedbased on both the result of comparison of the signal of detected bladestress with a predetermined permissible value of blade stress and theresult of comparisons of the detected signals of the operatingconditions with predetermined values of operating conditions and thecalculation result is outputted to said blade length adjustingmechanism.

Further, it is preferable that said operating condition detectorsinclude at least one among a wind speed detector for detecting the speedof the wind acting on the wind turbine, a rotation speed detector fordetecting the rotation speed of a rotating component of the wind turbineincluding the rotor, and a load detector for detecting the load of thewind turbine, a blade stress detector is provided for detecting thestress occurred in the blade, and said blade length controller comparesthe signal of detected blade stress inputted from said blade stressdetector with a predetermined permissible stress, and compares thesignal of detected wind speed from said wind speed detector with apredetermined permissible value of wind speed, or compares the signal ofdetected rotation speed from said rotation speed detector with apredetermined permissible value of rotation speed, or compares thesignal of detected load from said load detector with a predeterminedpermissible value of load, calculates the amounts of active annularplane area and blade length to be adjusted for optimal operationconcerning at least one among wind speed, rotation speed, and load whilemaintaining the blade stress at or near the predetermined permissiblestress, based on the result of said comparisons and outputs the resultto said blade length adjusting mechanism.

The seventh means of the present invention is an operating method of thewind turbine with an active annular plane area control mechanismcomprising a plurality of blades attached to a rotor for transmittingthe wind force acting on the blades to the output shaft of the windturbine connected to the rotor, each of said blades being configured sothat blade length can be changed in the total length of the blade or ina certain length from the middle up to the tip of the blade, wherein theoperating condition of the wind turbine is detected, the detectedoperating condition signals are compared with predetermined permissiblevalues, the amounts of active annular plane area and blade length to beadjusted for optimal operation concerning the operation condition arecalculated, and the blade length is changed according to the calculationresult.

It is preferable in the seventh means that the blade stress is detected,the detected signal of the blade stress is compared with a predeterminedpermissible blade stress, the amounts of active annular plane area andblade length to be adjusted for optimal operation concerning both saidoperation condition and said blade stress are calculated, and the bladelength is changed according to the calculation result.

According to the sixth and seventh means, each of said blades iscomposed such that a certain length of the blade from the middle to thetip thereof is variable and active annular plane area is changeable bychanging the length of the variable length blade part by means of theblade length adjusting mechanism, the speed of the wind acting on thewind turbine is detected by the wind speed detector, the rotation speedof a rotating component including the rotor is detected by the rotationspeed detector, the load (output) of the wind turbine is detected by theload detector, further the stress of the blade is detected by the bladestress detector, and the detected values are inputted to the bladelength controller.

The blade length controller compares said detected wind speed with thepredetermined permissible wind speed, or compares the detected rotationspeed with the predetermined permissible rotation speed, or compares thedetected load with the predetermined permissible load, and furthercompares the detected blade stress with the predetermined permissibleblade stress, and calculates the active annular plane area and bladelength to be adjusted based o the result of the comparisons.

Further, the blade length controller controls the blade length adjustingmechanism based on the calculated active annular plane area and bladelength as follows.

When the detected wind speed is higher than the permissible wind speed,the active annular plane area is decreased by decreasing the bladelength, and when the detected wind speed is lower than the permissiblewind speed, the active annular plane area is increased by increasing theblade length. When the detected rotation speed is higher than thepermissible rotation speed, the active annular plane area is decreasedby decreasing the blade length, and when the detected rotation speed islower than the permissible rotation speed, the active annular plane areais increased by increasing the blade length. When the detected load ishigher than the permissible load, the active annular plane area isdecreased by decreasing the blade length, and when the detected load islower than the permissible load, the active annular plane area isincreased by increasing the blade length. Further, when the detectedblade stress is higher than the permissible blade stress, the activeannular plane area is decreased by decreasing the blade length, and whenthe detected blade stress is lower than the permissible blade stress,the active annular plane area is increased by increasing the bladelength.

By controlling the blade length through the blade length controllermentioned above, the lengths of the blades are adjusted so that theactive annular plane area is optimal corresponding to the operatingconditions such as wind speed, rotation speed and load of the windturbine, and the output of the wind turbine can be always maintained ata maximum output level.

Further, according to the sixth and seventh means, as an active annularplane area can be controlled so that it is optimal for both theoperating conditions such as wind speed, rotation speed and load of thewind turbine and for blade stress, the occurrence of excess blade stressof the rotating component due to sudden increase in wind speed or loadis suppressed, and the occurrence of fatigue failure of said rotatingcomponents can be prevented.

Therefore, according to the sixth and seventh means, the wind turbinecan be operated while always automatically controlling blade length sothat the occurrence of fatigue failure of the rotating components suchas the blades and rotor, and at the same time the wind turbine isoperated with the optimal active annular plane area which insures amaximum of the wind turbine output while avoiding the fatigue failure.Accordingly, the operation of the wind turbine is possible with anoptimal maximum output with elongated fatigue life of the rotatingelements such as the blades and rotor.

The eighth means of the present invention is a wind turbine with anactive annular plane area control mechanism comprising a plurality ofblades attached to a rotor head for transmitting the wind force actingon the blades to the output shaft of the wind turbine connected to therotor head, wherein each blade is attached to an end side of aconnecting elbow of a certain bent angle, the other end side is attachedto the periphery of the rotor head for rotation, a connecting elbowdriving device is provided for rotating each of said connecting elbows,and the blades can be tilted in the direction of the axis of the rotorhead to adjust active annular plane area.

It is preferable that there are provided a wind speed detector fordetecting the speed of the wind acting on the blades, and a controllerwhich calculates average wind speed during a certain period of time fromthe wind speed detected continuously by said wind speed detector and thetilt angle of the blades optimal for the average wind speed and controlssaid connecting elbow driving device so that the blades are tilted tothe calculated angle.

As the operating method of the wind turbine with an active annular planearea control mechanism comprising a plurality of blades attached to arotor head for transmitting the wind force acting on the blades to theoutput shaft of the wind turbine connected to the rotor head, it ispreferable that the speed of the wind acting on the blades is detected,average wind speed during a certain period of time is calculated fromthe wind speed detected continuously by said wind speed detector, theactive annular plane area optimal for the average wind speed iscalculated, and the rotation angle of said connecting elbows is adjustedso that active annular plane area becomes equal to said calculated valuethrough composing such that each blade is attached to each of aplurality of connecting elbows attached to the rotor head for rotationso that the blade is capable of being tilted in the direction of theaxis of rotation of the rotor head by rotating said connecting elbow.

In the eighth means, it is preferable that said connecting elbow drivingdevice comprises a ring gear fixed to said other end of the connectingelbow concentric with the axis of rotation thereof, a pinion meshingwith the ring gear, a reversible motor for rotating the pinion, and amotor control device for controlling the rotation of the motor accordingto the output signal from said controller.

According to the eighth means, the speed of the wind acting on theblades is detected by the wind speed detector and inputted to thecontroller, and the controller calculates the average wind speed duringa certain time period from the wind speed detected continuously by saidwind speed detector and also calculates an active annular plane area theoptimal wind turbine output for the average wind velocity from thepredetermined relation between average wind speed and wind turbineoutput, and determines the active annular plane area based on saidoutput.

The wind turbine is provided with the blade tilting mechanism whichcomprises connecting elbows to each of which is attached the blade andeach of which is attached rotatably to the periphery part of the rotorhead such that each blade is tilted by the rotation of each connectingelbow to change the tilt angle of the blade in order to change activeannular plane area, and said controller calculates the rotation angle torealize said calculated active annular plane area and output it to theconnecting elbow driving device of said blade tilting mechanism.

The connecting elbow driving device rotates the connecting elbow tochange the tilt angle of the blade so that the tilt angle is equal tosaid calculated angle and keeps the blade at the position.

Thus, according to the eighth means, said controller allows saidconnecting elbow to be rotated to the position with which the blades areat right angle to the axis of rotation of the rotor head, accordinglyactive annular plane area is at maximum when average wind speed is lowerthan the predetermined lower limit value so that a maximum power istaken-in from wind. In this case, as wind speed is low, fatigue failureof the rotating components such as the blades and rotor does not occurby increasing the active annular plane area to the maximum.

When average wind speed is higher than the predetermined higher limitvalue, the connecting elbow is rotated to the position where the bladesare tilted toward the axis of rotation of the rotor to decrease theactive annular plane area in order to avoid occurrence of fatiguefailure of the rotating components.

When average wind speed is between said lower limit and higher limit,the output of the wind turbine is determined according to the averagewind speed and the blades are tilted to a position with which saiddetermined power is obtained, and the wind turbine is operated with anoptimal output taking into consideration fatigue failure of the rotatingcomponents.

By this, the wind turbine can be operated with the tilt angle of theblades adjusted and fixed at the position so that the output is amaximum while avoiding the occurrence of fatigue failure of the rotatingcomponents such as the blades and rotor.

Further, by changing the distance from the axis of rotation of theconnecting elbow to the end face thereof for attaching the blade, thetip diameter of the blade can be changed. Therefore, the active annularplane area can be changed by preparing several connecting elbowsdifferent in said distance and only changing the connecting elbowwithout preparing blades of different blade length.

Further, according to the eighth means, the connecting elbow drivingdevice can be composed so that the connecting elbows are controlled tobe rotated to the rotational position determined by the controller byrotating them by the driving motor via the motor control device.Therefore, a simple and low-cost connecting elbow driving device can beobtained without using hydraulic devices operated by oil hydraulicpressure or air pressure.

Further, according to the eighth means the adjustment of active annularplane area is possible by providing the blade tilting mechanism composedof said connecting elbow driving device and connecting elbowindependently for each blade for adjusting the active annular plane areaby changing the tilt angle of each blade by rotating the connectingelbow through the connecting elbow driving mechanism, and it is possibleto adjust the tilt angle of each blade to an optimal position takinginto consideration the output power of the wind turbine and fatiguelimit of the rotating components.

As has been described above, according to the eighth means, the problemthat may occur with conventional wind turbines having no adjusting meansfor adjusting the active annular plane area, i.e., the occurrence offatigue failure of the rotating components such as the blade and rotordue to excessive high speed wind sometimes experienced by a gust of windis prevented, and the wind turbine can be operated with a maximum outputwhile avoiding the occurrence of fatigue failure of the rotatingcomponents such as the blades and rotor by adjusting active annularplane area by changing the tilt angle of the blades through changing therotation angle of each connecting elbow according to the speed of thewind acting on the blades.

Therefore, according to the eighth means, the wind turbine can beoperated while always automatically controlling blade length so that theoccurrence of fatigue failure of the rotating components such as theblades and rotor and at the same time with the optimal active annularplane area which insures a maximum of the wind turbine output within therange capable of evading the fatigue failure. Accordingly, the operationof wind turbine is possible with an optimal maximum output withelongated fatigue life of the rotating elements such as the blades androtor.

The ninth means of the present invention is a wind turbine with anactive annular plane area control mechanism comprising a plurality ofblades attached to a rotor head for transmitting the wind force actingon the blades to the output shaft of the wind turbine connected to therotor head, wherein a blade tilting mechanism is provided for tiltingthe blades in the direction of the axis of rotation of the rotor head tochange the active annular plane angle.

It is preferable that there are provided a wind speed detector fordetecting the speed of the wind acting on the blades, and a controllerwhich calculates average wind speed during a certain period of time fromthe wind speed detected continuously by said wind speed detector and thetilt angle of the blades optimal for the average wind speed and controlssaid blade tilting mechanism so that the blades are tilted to thecalculated angle.

It is also preferable that said blade tilting mechanism comprises afluid pressure actuator which is fixed to the rotor head so that theoutput shaft thereof moves in the direction of the axis of rotation ofthe rotor head, and a plurality of blade link each of which is supportedvia the supporting shaft fixed to the rotor head for swinging, an endpart of each link being connected to the output shaft of said fluidpressure actuator and the other end being connected to each blade, andthe tilt angle of the blades can be changed by swinging said blade linkaround said supporting shaft through the reciprocation of the outputshaft of said fluid pressure actuator.

Further, it is preferable that said blade tilting mechanism comprises aservomotor fixed to the rotor head and having an output shaft having amale screw thread part, and a plurality of blade links each of which issupported via the supporting shaft fixed to the rotor head for swinging,an end part of each link being connected to a blade link guide engagedwith the male screw thread of the output shaft of said servomotor, theother end being connected to each blade, and the tilt angle of theblades can be changed by swinging said blade link around said supportingshaft through the rotation of the output shaft of said servomotor.

Yet further, it is preferable that said blade tilting mechanismcomprises a plurality of blade links each of which is supported via thesupporting shaft fixed to the rotor head for swinging, and fluidpressure actuators each bridging between the protrusion extending fromthe center of the end of the rotor head and each blade link for changingthe blade tilt angle in the direction of the axis of rotation of therotor head by the extension and contraction of said actuator.

The tenth means of the present invention is an operating method of thewind turbine with an active annular plane area control mechanismcomprising a plurality of blades attached to a rotor head fortransmitting the wind force acting on the blades to the output shaft ofthe wind turbine connected to the rotor head, wherein the speed of thewind acting on the blades is detected, average wind speed during acertain period of time is calculated from the wind speed detectedcontinuously by said wind speed detector, the active annular plane areaoptimal for the average wind speed is calculated, and the rotation angleof said connecting elbow is adjusted so that active annular plane areabecomes equal to said calculated value through composing such that eachblade is capable of being tilted in the direction of the axis ofrotation of the rotor head.

According to the ninth and tenth means, the speed of the wind acting onthe blades is detected by the wind speed detector and inputted to thecontroller, and the controller calculates the average wind speed duringa certain time period from the wind speed detected continuously by saidwind speed detector and also calculates the active annular plane areathe optimal wind turbine output for the average wind velocity from thepredetermined relation between average wind speed and wind turbineoutput, and determines the active annular plane area based on saidoutput.

The wind turbine is provided with the blade tilting mechanism forchanging the active annular plane area by tilting the blades toward theaxis of rotation of the rotor head, and said controller calculates thetilt angle of the blades to realize said calculated active annular planearea and output it to the actuator of said blade tilting mechanism.

The blade tilting mechanism tilts the blades so that said calculatedactive annular plane area is realized by the tilting and keeps the bladeat the position.

Thus, said controller allows the blades to be at right angle to the axisof rotation of the rotor head, accordingly active annular plane area isat maximum when average wind speed is lower than the predetermined lowerlimit value so that a maximum power is taken-in from wind. In this case,as wind speed is low, fatigue failure of the rotating components such asthe blades and rotor does not occur by increasing the active annularplane area to the maximum.

When average wind speed is higher than the predetermined higher limitvalue, the blades are tilted toward the axis of rotation of the rotor todecrease active annular plane area in order to evade the occurrence offatigue failure of the rotating components.

When average wind speed is between said lower limit and higher limit,the output of the wind turbine is determined according to the averagewind speed and the blades are tilted to a position with which saiddetermined power is obtained, and the wind turbine is operated with anoptimal output taking into consideration fatigue failure of the rotatingcomponents.

By this, the wind turbine can be operated with the tilt angle of theblades adjusted and fixed at the position so that the output is amaximum within the range of evading the occurrence of fatigue failure ofthe rotating components such as the blades and rotor.

Further, according to the ninth and tenth means, the blades can beadjusted to the same tilt angle in synchronism with each other by asingle or pair of fluid pressure actuators or a single or a pair ofservomotor, so the blade tilting mechanism is of simple construction,and as the connection between the output shaft of the fluid pressureactuator or servomotor is of link connection, variations in the tiltangles of the blades are small and blade tilt angle control can bepossible with high accuracy.

The adjustment of the active annular plane area is possible by changingindependently the tilt angle of each blade by means of the fluidpressure actuator and it is possible to adjust the tilt angle of eachblade to an optimal position taking into consideration the output powerof the wind turbine and fatigue limit of the rotating components.

As has been described above, according to the ninth and tenth means, theproblem that may occur with conventional wind turbines having noadjusting means for adjusting active annular plane area, i.e., theoccurrence of fatigue failure of the rotating components such as theblade and rotor due to excessive high speed wind sometimes experiencedby a gust of wind is prevented, and the wind turbine can be operatedwith a maximum output while avoiding the occurrence of fatigue failureof the rotating components such as the blades and rotor by adjusting theactive annular plane area by changing the tilt angle of the bladesaccording to the speed of the wind acting on the blades.

Therefore, according to the ninth and tenth means, the wind turbine canbe operated while always automatically controlling blade length so thatthe occurrence of fatigue failure of the rotating components such as theblades and rotor and at the same time with the optimal active annularplane area which insures a maximum of the wind turbine output within therange capable of evading the fatigue failure. Accordingly, the operationof wind turbine is possible with an optimal maximum output withelongated fatigue life of the rotating elements such as the blades androtor.

It is suitable to use an oil hydraulic actuator or pneumatic actuator assaid fluid pressure actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse sectional view of the 1^(st) embodiment of thewind turbine capable of moving blades in radial direction according tothe present invention (sectional view taken in the direction of arrowsB—B of FIG. 2)

FIG. 2(A) is a partial vertical longitudinal sectional view of the windturbine of FIG. 1, and

FIG. 2(B) is an enlarged detail of portion Z of FIG. 2(A).

FIG. 3 is a transverse sectional view of the 2^(nd) embodiment of thewind turbine corresponding to FIG. 1.

FIG. 4 is a transverse sectional view of the 3^(rd) embodiment of thewind turbine corresponding to FIG. 1.

FIG. 5 is a transverse sectional view of the 4^(th) embodiment of thewind turbine corresponding to FIG. 1.

FIG. 6 is a partial vertical longitudinal sectional view of saidembodiments of the wind turbine.

FIG. 7 is a transverse sectional view of the 5^(th) embodiment which isa darrieus type, showing the mechanism of spreading blades in radialdirection.

FIG. 8 is an enlarged detail of portion Y in FIG. 7.

FIG. 9 is a diagrammatic illustration of the blade length adjustingmechanism of the 6^(th) embodiment of the wind turbine with variablelength blades according to the present invention, (A) is a sectionalview taken in the direction of arrows D—D of FIG. 14, and (B) is asectional view taken in the direction of arrows A—A of FIG. 9(A).

FIG. 10 is a partial transverse sectional view showing the constructionof the blade length adjusting mechanism of the 7^(th) embodiment.

FIG. 11 is a partial transverse sectional view showing the constructionof the blade length adjusting mechanism of the 8^(th) embodimentcorresponding to FIG. 2.

FIG. 12 is a partial transverse sectional view showing the constructionof the blade length adjusting mechanism of the 9^(th) embodimentcorresponding to FIG. 2.

FIG. 13 is a partial transverse sectional view showing the constructionof the blade length adjusting mechanism of the 9^(th) embodiment, (A)shows the construction, and (B) is a sectional view taken in thedirection of arrows B—B of FIG. 13(A).

FIG. 14 is a front view of a wind turbine to which the present inventionis applied.

FIG. 15 shows the control block diagram of blade length adjustingmechanism of the 11^(th) embodiment according to the present invention.

FIG. 16 is a front view of the wind turbine of said 11^(th) embodimentshowing locations of detectors.

FIG. 17 illustrates when the 8^(th) embodiment is equipped with themotor control device and blade length control device for controllingactive annular plane area.

FIG. 18 is a front view of the 12^(th) embodiment of the wind turbineaccording to the present invention.

FIG. 19 is a side view of the wind turbine of FIG. 18 viewed in thedirection of arrow B of FIG. 18

FIG. 20 is an enlarged sectional view taken in the direction of arrowsA—A of FIG. 18.

FIG. 21 is an enlarged detailed sectional view of portion Z of FIG. 18,showing the detail of the pitch angle control device.

FIG. 22(A) is a control block diagram of the active annular plane areaadjusting device, FIG. 22(B) is a graph showing output curves of thewind turbine.

FIG. 23 is a partial sectional view of the active annular plane areaadjusting device of the 13^(th) embodiment of the wind turbine accordingto the present invention (sectional view taken in the direction ofarrows B—B of FIG. 24).

FIG. 24 is a front view of the active annular plane area adjustingdevice of FIG. 23 with a partially sectional view in the direction ofarrow A—A of FIG. 23.

FIG. 25 is a partial sectional view of the active annular plane areaadjusting device of the 14^(th) embodiment, corresponding to FIG. 23.

FIG. 26 is a partial sectional view of the active annular plane areaadjusting device of the 15^(th) embodiment, corresponding to FIG. 23.

FIG. 27 is a schematic side view of the downwind type wind turbine towhich the present invention is applied.

FIG. 28(A) is a control block diagram of the active annular plane areaadjusting device according to the present invention, FIG. 28(B) is agraph showing output curves of the wind turbine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will now be detailedwith reference to the accompanying drawings. It is intended, however,that unless particularly specified, dimensions, materials, relativepositions and so forth of the constituent parts in the embodiments shallbe interpreted as illustrative only not as limitative of the scope ofthe present invention.

Referring to FIG. 6 showing upper half of the wind turbine of the first,second, and third embodiments, reference numeral 2 is a rotor formedinto a cylindrical shape and with a plurality of blades 1 (three bladesin this example) attached on the periphery at an equal spacing along thecircumference by the means described later, the rotor having a rotorshaft 3 in the rear portion, a blade shifting mechanism as describedlater being provided in the hollow space 02 of the rotor.

Reference numeral 4 is an entrance guide element fixed to a wind turbinesupport not shown in the drawing, the outer diameter of the rear portionof the entrance guide adjacent the rotor being about the same with thatof the rotor. Reference numeral 5 is a rear case also fixed to said windturbine support, the outer diameter of the front portion of the rearcase adjacent the rotor being about the same with that of the rotor.

Said rotor 2 is supported by said entrance guide element 4 via a bearing6 at the front side thereof and supported by said rear case 5 via abearing 7 at the rear side thereof for rotation around the center axis02 of the rotor.

Referring to FIG. 1˜2 showing the first embodiment, the sliding portion1 a formed at the root of each of said blades 1 is inserted forreciprocal movement in each of holes 2 a drilled in said cylindricalrotor 2 in radial direction at equal spacing.

At the middle between adjacent blades are drilled three holes 2 b (themay be a plurality of holes) on the circumference of the rotor and anend portion of each of screw bars 10, each having a threaded part in themiddle thereof, is inserted in each of the holes 2 b for rotation andnot movable in the direction of its axis. Reference numeral 16 aresleeves (nuts) screwed to said threaded parts of said screw bars 10.Reference numeral 13 are links each of which is fixed to the root ofeach of the blades 1, both ends of each link 13 being connected to anend of each of links 12 by means of pins 14, the other end of each link12 being connected to each of links 17 each being fixed to each sleeve16 via each of pins 15.

In FIG. 2, reference numeral 23 is a motor fixed to said rear case 5 orsaid entrance guide element 4. Reference numeral 20 is a bevel gearconnected to the output shaft of said motor 23. The bevel gear 20 mesheswith each of pinions formed at the other end of each of said screw bars10 and each screw bar 10 is rotated by the rotation of said bevel gear20.

Reference numeral 22 is a blade pitch angle controlling element forvarying the pitch angle, 21 is a bevel gear mechanism for transmittingdriving force to change the pitch angle, 22 a is a connecting shaft forconnecting said bevel gear mechanism with said blade pitch anglecontrolling element 22. The connecting shaft 22 a and blade pitch anglecontrolling element 22 are connected by spline connection (in FIG. 2(B),1 a is a female spline of the blade pitch angle controlling element 22and 22 b is a male spline of the connecting shaft 22 a side), and saidblade pitch angle controlling element 22 can be moved in a radialdirection relative to the rotor 2 together with the blade 1. Thestructure of said blade pitch controlling element is known and detailedexplanation is omitted.

Reference numeral 91 is a wind speed detector for detecting the speed ofwind acting onto the blade 1, 90 is a motor control device. The motorcontrol device 90 calculates the required active annular plane area andthe radial blade position corresponding with the required active annularplane area based on the detected signal of wind speed inputted from saidwind speed detector 91 as mentioned later, and outputs the result tosaid motor 23.

Wind flows from the annular plane of area S to act on the blades 1 androtate the rotor 2, then flows out guided by the periphery of the rearcase 5. The rotating force of the rotor 2 is transmitted via the rotorshaft to drive the driven machinery such as a generator.

Next, the controlling of radial movement of said blade 1 will beexplained.

The wind speed detected by said wind speed detector 91 is inputted tosaid motor control device 90. In the motor control device 90 are setbeforehand a relation 1 which is the relation between the output P ofthe wind turbine, wind speed V, and active annular plane area S, asshown previously by equation (2) and a relation 2 which is the relationbetween the limit wind speed which induces fatigue failure of therotating elements such as the blades and rotor and an active annularplane area S.

When it is judged by the motor control device 90 that with presentradial position of blades the detected wind speed is smaller than thewind speed for outputting required power of the wind turbine, the activeannular plane area and radial blade position required to output therequired power under the detected wind speed are calculated, and themotor control device 90 outputs a signal to said motor 23 to move theblades to the calculated radial position.

The motor 23 rotates the pinion 11 via the bevel gear 20 by the amountcorresponding to the signal from the motor control device 90. The screwbar 10 is rotated by the rotation of the pinion, and the sleeve 16 movesalong the screw bar 10 to move the blade 1 in a radial outward directionvia the links 12 and 13, resulting in increased active annular planearea.

By this operation, the active annular plane area is adjusted for thewind turbine to output the required output.

Further, when the detected wind speed exceeds said limit speed, themotor control device 90 calculates the active annular plane area andradial blade position corresponding thereto for the limit wind speed andoutput a signal to the motor 23 to move the blades to the calculatedradial position.

The motor 23 moves the blade 1 in a radially inward direction via thebevel gear 20 pinion 11, screw bar 10, sleeve 16, and links 12 and 13 toreduce the active annular plane area. By this operation, the activeannular plane area is adjusted for the wind turbine to be operatedwithin the range of wind active annular plane area with which theoccurrence of fatigue failure can be avoided.

As mentioned above, according to the first embodiment, the blades aremoved in a radially outward directions to increase the active annularplane area as detected wind speed decreases, and the blades are moved ina radially inward directions to decrease the active annular plane areaas detected wind speed increases. By controlling the radial position ofthe blades like this, the wind turbine can be operated so that theoutput as high as possible is obtained while avoiding the occurrence offatigue failure of the rotating components such as the blades and rotorunder the present wind speed.

Referring to FIG. 3 showing the second embodiment, a supporting element41 is provided in the center of a rotor 2, and the supporting element 41and the sliding portion 1 a of each blade 1 are connected by anextendible and contractible link mechanism composed of a pair of linkset 31, 37 and 34, 42 connected by means of pins 33, 35, 44, and 33, 43,44.

A screw bar 32 is provided between a bracket 38 and 36, which are fixedto each of the links 31 for adjacent two blades, an end side of thescrew bar 32 being screwed into a nut 39 fixed on said bracket 38, theother end side being supported for rotation by said bracket 36. At theend of this other end side is fixed a pinion 40 which is rotated by amotor 45 via a pinion fixed to the shaft of the motor 45.

With the second embodiment, when said screw bar 32 is shifted, forexample, in the direction of arrow Y by rotating the pinion 40 therotation of the motor 45, said pair of link set 34, 42 and 31, 37 aremade narrower and the blade 1 is moved in the radial direction of arrowZ.

By this operation, the protrusion of the blade 1 from the outercircumference of the rotor 2 is increased and the active annular planearea increases. To decrease the active annular plane area, said pinion40 is rotated in the reverse direction to make the pair of link set 34,42 and 31, 37 opened wider by means of the screw bar 32 and the blade 1is moved radially inward.

In the case of the third embodiment shown in FIG. 4, a supportingelement 57 is provided in the center of the rotor 2, and two rings, aninner ring 56 and an outer ring 54 capable of reverse rotation relativeto each other are provided. Said supporting element 57, said outer ring54, and the sliding portion 1 a of the blade 1 are connected by twolinks 52 and 58 via pins 53 and 59, and said inner ring 56 and saidsliding portion 1 a of the blade 1 are connected by a link 51 via pins50 and 53.

According to the third embodiment, when said inner ring 56 is rotatedfor example in the direction of arrow W, the left-side link 52, 58 andthe right-side link 51 are made narrower and the blade 1 is moved in theradial direction of arrow X.

By this operation, the protrusion of the blade 1 from the outercircumference of the rotor 2 is increased and the active annular planearea increases. To decrease the active annular plane area, said innerring 56 is rotated in the reverse direction to made the left-side link52, 58 and the right-side link 51 opened wider to move the blade 1radially inward.

In the 4^(th) embodiment shown in FIG. 5, reference numeral 105 is aslider receiver fixed to the rotor 2 with its center axis passingthrough the center of the rotor 2, and 103 is a slider inserted in saidslider receiver 105 reciprocation, a screw hole 103 a being provided atthe center of the slider 103.

Reference numeral 101 is a motor, 102 is a screw bar fixed to the outputshaft of the motor 101, the screw bar 102 being screwed into the screwhole 103 a of said slider 103.

A link 107 is fixed to the inside end of the sliding portion 1 a of theblade 1.

Reference numeral 106 is a swing link, an end thereof being formed intoa spherical or cylindrical shape and received in a spherical orcylindrical bearing part 104 provided in said slider 103 so that theswing link 106 can swing around the bearing part 104. The other end partof the swing link 106 has an elongated hole 108 through which the swinglink is connected to the link 107 fixed to the blade 1 via a pin 109.

Reference numeral 111 is a supporting link fitted for reciprocation tosaid screw bar 102. Reference numeral 110 is a link receiver fitting tosaid swing link 106 to guide the swing link 106. The lower end part ofthe link receiver 110 is connected to the outer end part of saidsupporting link 111 via a pin 114. Reference numeral 112, 113 arestoppers provided on said screw bar 102 at a spacing, said supportinglink being capable to reciprocate between the stoppers 112, 113. Two setof link mechanisms are configured to adjust the radial blade position oftwo blade as shown in FIG. 5.

With this construction of the 4^(th) embodiment, when the screw bar 102is rotated, for example, in the direction of arrow N by the motor 101,the slider 103 moves along the slider receiver 105 to the direction ofarrow M, the swing links 106 swing around the bearing parts 104 in thedirection of arrows L guided by the link receiver 110, and the links 107move to the direction of arrows J guided by the elongated holes 108 tomove the blades 1 radially inward respectively.

By this operation, the protrusion of the blade 1 from the outercircumference of the rotor 2 is decreased and the active annular planearea decreases. When the screw bar 102 is rotated in the reversedirection, the protrusion of the blade 1 from the outer circumference ofthe rotor 2 is increased and the active annular plane area increases.

The 5^(th) embodiment shown in FIG. 7, 8 is a case where the presentinvention is applied to a darrieus type wind turbine. In the drawing,reference numeral 61 is a turbine shaft erected upright. Referencenumeral 75 refers to screw bars erected upright parallel to the verticalturbine shaft 61 in neighboring position of both sides of the shaft 61.Each of the screw bars 75 has right-hand thread parts 75 a and left-handthread parts 75 b cut by turns along the bar.

Reference numeral 66 refers to a plurality of supporting elementsprovided along the direction of axis of the turbine shaft 61 (threesupporting elements in this example), and a plurality of sets of blades60 are provided between the adjacent supporting elements 66 and they areattached to the elements 66 by means of pins 69. The blades 60 areprovided along the turbine shaft 61 in one stage or in a plurality ofstages (in two stages in the example).

Three pairs (one pair or a plurality of pairs are acceptable) ofshifting elements 62, 63 are provided. One of each pair has a right-handfemale screw thread on both end sides, each of the female screw threadbeing engaged with the right-hand thread part 75 a of each of said screwbars 75. The other of each pair has a left-hand female screw thread onboth end sides, each of the female screw thread being engaged with theleft-hand thread part 75 b of each of said screw bars 75. Each one ofthe pair moves in the direction contrary to each other by the rotationof the screw bars. Each of the shifting elements 62, 63 is attached tothe turbine shaft 61 by means of a key 77 so that the elements can bemoved in the direction of the axis of the screw bar 75 but is notrotatable. Links 76, 64 compose a pair of links connecting saidsupporting element 66 to said pair of shifting elements 62, 63 via pins67, 68 and 65, 70.

Said turbine shaft 61 is supported for rotation by a case 71 fixed onthe ground via bearings 72 and 73. Reference numeral 74 is a electricgenerator driven by the wind turbine.

Referring to FIG. 8, reference numeral 78 is a motor, 79 is a outputshaft gear of the motor 78, the output shaft gear 79 meshing with thescrew bar gear 80 fixed to the lower end part of one of said screw bars75. Sprocket 81 is fixed to the lower end part of each of the screw bars75, and a chain 82 runs between the sprockets. The rotating force ofsaid motor 78 is transmitted by the chain 82 so that the rotation speedof both screw bars is the same.

Reference numeral 91 is a wind speed detector for detecting the speed ofwind acting on the wind turbine. Reference numeral 90 is a motor controldevice, which calculates the required active annular plane area of theblades 60 and the blade radial position corresponding to the requiredannular plane area based on the detected wind speed inputted from thewind speed detector 91 and controls the motor driving according to themethod described later.

With the 5^(th) embodiment, when the detected wind speed is inputtedfrom said wind speed detector to the motor control device 90, the motorcontrol device 90 calculate the required active annular plane area ofthe blades 60 and the blade radial position corresponding to therequired annular plane area based on the detected wind speed for thedetected wind speed.

The control of the active annular plane area of the blades 60 and theblade radial position is performed, similarly in the case of the firstto third embodiment, so that the blades 60 are moved in a radiallyoutward direction to increase the active annular plane area of theblades 60 as the detected wind speed decreases, and the blades 60 aremoved in a radially inward direction to decrease the active annularplane area of the blades 60 as the detected wind speed increases.

To move the radial position of blades 60 outward when detected windspeed decreases, the motor 78 is driven by the control signal from saidmotor control device 90 to rotate the left and right bar 75, 75 insynchronism with each other via the output shaft gear 79, screw bar gear80, chain 82, and sprocket 81, and the elements 62 and 63 of theshifting element pair, each of which is engaged with the right-handthread part 75 a and the left-hand thread part 75 b of the screw bars 75respectively, are caused to be drawn nearer. By this action, thesupporting elements 66 supporting the blades 60 are moved radiallyoutward via the pairs of links 64 and the radius of rotation of theblades 60 is increased.

To move the radial position of blades 60 inward when detected wind speedincreases, the motor 78 is driven to rotate in the reverse direction,the elements 62 and 63 of the shifting element pair, each of which isengaged with the right-hand thread part 75 a and the left-hand threadpart 75 b of the screw bars 75 respectively, are caused to be drawnremoter. By this action, the supporting elements 66 supporting theblades 60 are moved radially inward via the pairs of links 64 and theradius of rotation of the blades 60 is decreased.

According to the 1^(st)˜5^(th) embodiments, it is possible to controlthe radial position of blades 1 so that the radius of the radial bladeposition is increased by moving the blades radially outward as windspeed decreases and it is decreased by moving the blades radially inwardas wind speed increases. By controlling the radial position of theblades thusly, the wind turbine can be operated so that the output ashigh as possible is obtained while evading the occurrence of fatiguefailure of the rotating components such as the blades and rotor underthe present wind speed.

Here, referring to FIG. 14 showing a wind turbine to which the presentinvention is applied, reference numeral 1103 is a rotor having aplurality of blades 100 (three blades in this example) attached on theperiphery thereof at an equal spacing in the circumferential directionand having a rotor shaft 1102 fixed to the rear end thereof. Said blades100 are each composed of a blade body part 102 fixed to said rotor 1103and a variable length blade part 101 which is attached to said bladebody part 102 capable of being moved radially in the direction of bladelength. Reference numeral 1101 is a support for supporting the windturbine.

Referring to FIG. 9 showing the 6^(th) embodiment, reference numeral 101is a variable blade length part formed in an extendible and contractiblebellows shape, which configured as follows.

Reference numeral 101 a is a hull formed in a bellows shape in thedirection of blade length, 103 a, 103 b, 103 c are air chambers in saidhull 101 a, each of the air chambers being an independent chamberseparated by partition walls 104. As shown in FIG. 9(B), hull 101 a isformed in a profile such that the shape of cross section perpendicularto the blade length direction is a form capable of effecting aerodynamiclift. A top cover 114 covers the top of the hull 101 a.

Reference numeral 108 is a wire passing through the air chambers 103 a,103 b, and 103 c, 113 is a wire drum winding said wire 108, 10 is amotor for rotating the wire drum 113 to push or draw the wire 108 in theblade length direction. Reference numeral 107 are seal elements providedbetween the outer surface of the wire 108 and partition walls 104 forsealing each of the air chambers 103 a, 103 b, and 103 c.

Reference numeral 111 is an air supplying device for producingpressurized air, 109 is a flexible air tube connected to the air outletof the air supplying device, the tube 109 being made of rubber or softsynthetic resin, etc. The flexible air tube 109 is configured so that itcan be moved or deformed as the variable length blade part 101 expandsor contracts. Reference numeral 105 represents air supply openings ofthe parts branched off from flexible air pipe 109, each of the openingscommunicating to the air chamber 103 a, 103 b, and 103 c respectively.Reference numeral 106 represents air valves for opening/closing said airsupply openings 105. Reference numeral 107′ represents seal elements forsealing the air chambers 103 a, 103 b, 103 c.

Reference numeral 112 is an air control device which controls theopening/closing of said air valves 106 and also controls the operationof said air supplying device 111.

With the 6^(th) embodiment, when wind speed decreases, the air supplyingdevice 111 is operated to produce required air pressure according to thesignal from the air control device 112 and the air valves 106 are openedto supply pressurized air from the air supplying device 111 to the airchambers 103 a, 103 b, 103 c. On the other hand, the wire drum 113 isrotated by the motor 111 to draw out the wire 108.

By this operation, the volume of each air chamber 103 a, 103 b, and 103c is increased, and the variable blade length part 101 formed in abellows shape is extended radially outward resulting in increaseddiameter of the blade tip, and therefore the active annular plane areais increased.

When wind speed increases, air pressure of the air supplying device 111is reduced or the air pressure is released and some or all of the airvalves 106 are closed to reduce the pressure of some or all of the airchambers 103 a, 103 b, and 103 c.

On the other hand, the wire drum 113 is rotated in the reverse directionto rereel the wire 108 to draw the top cover 114 fixed to the extremityof the wire 108.

By the operation, the volume of each air chamber 103 a, 103 b, and 103 cdecreases, and the variable blade length part formed in a bellows shapeis contracted in inward resulting in decreased diameter of the bladetip, and therefore the active annular plane area is decreased.

According to the 6^(th) embodiment, the effective length of the variablelength part 101, accordingly the effective length of the blades can bevaried to vary the active annular plane area, by supplying pressurizedair from the air supplying device 111 by way of a flexible air tube 109or exhausting the air to or from the air chambers 103 a, 103 b, and 103c, which are formed in the variable blade length part 1 formed in abellows shape extendible and contractible in the radial direction of therotor 1103, through opening/closing the air valves 106 by the commandfrom the air control device 112 and at the same time by varying thediameter of the blade tip through extending or contracting the variableblade length part 101 by drawing out or in by means of a motor 110 thewire 108 connected to the top cover 114 fixed to the top end of thevariable blade length part 101.

By this, an active annular plane area can be adjusted to an optimal areain correspondence with wind conditions even in the operation of the windturbine, and the operation of the wind turbine can be performed so thatthe output is a maximum while avoiding the occurrence of fatigue failureof the rotating components such as the blades and rotor.

In FIG. 10 showing the 7^(th) embodiment, a blade 100 is divided intotwo to a blade body 102 fixed to said rotor 1103 and a variable lengthblade part 120 which define a part of blade from the middle to the tipof the blade 100.

Reference numeral 131 is a link fixed to the bottom part 129 of thevariable blade length part 120. The link 131 and variable blade lengthpart 120 can swing around a supporting shaft 132 guided by a guide face133 formed in the blade body 102, the supporting shaft 132 being fixedto said blade body 102 and supporting an end side of said link 131 forrotation.

Reference numeral 121 is a reversible motor, 122 is a pinion fixed tothe end part of the output shaft 121 a of the motor 121. Referencenumeral 123 is a rack meshing with said pinion 122, 124 is an actuatingshaft connected to the rack 123, 125 is a bearing for supporting theactuating shaft by the blade body 102.

Reference numeral 128 is a link for connecting the end part of theactuating shaft 124 to the other end part of the link 131 via pins 127and 30.

With the 7^(th) embodiment, when the pinion 122 is rotated in the normalor reverse direction of rotation by the motor 121, the rack 123 meshingwith the pinion 122 and the actuating shaft 124 fixed to the rack 123are reciprocated in the directions shown by double arrow Y. By thereciprocating motion of the actuating shaft, the link 131 is allowed toswing around the supporting shaft 132 via the link 128. By this, thevariable blade length part 120 of which the bottom part 129 is fixed tothe link 131 swing together with the link 131 around the supportingshaft 132 along the guide face 133.

That is, when the actuating shaft 124 is moved upward by the rotation ofthe motor 121, the link 131 and variable blade length part 120 areerected as shown with solid line in the drawing resulting in increasedtip diameter of the variable blade length part 120. When the motor 121is rotated in the reverse direction to move down the actuating shaft124, the link 131 and variable blade length part 120 are swung in thedirection of arrow Z of the drawing to be tilted as shown with chainline in the drawing resulting in decreased tip diameter of the variableblade length part 120.

As described above, according to the 7^(th) embodiment, the projectedarea of the surface of revolution of the blade in the direction of theaxis of rotation of the rotor, i.e., the active annular plane area, ischangeable by changing the tilt angle of the variable blade length part120 through swinging the variable blade length part 120 which issupported via the link 131 for rotation by the supporting shaft 132,around the supporting shaft 132 by means of the link 131.

Referring to FIG. 11 showing the 8th embodiment, a blade 100 is dividedin two to a blade body 102 fixed to said rotor 1103 and a variablelength blade part 140 which define a part of blade from the middle tothe tip of the blade 100.

Reference numeral 148 is a pair of slide bearing fixed to the blade body102. The sliding part 146 formed at the lower portion of the variablelength blade part 140 is fit to sliding surfaces of the pair of slidebearings 148 for sliding in the longitudinal direction of blade.

Reference numeral 141 is a reversible motor, 142 is a pinion fixed tothe end part of the output shaft 141 a of the motor 141. Referencenumeral 143 is rack meshing with said pinion 142. Reference numeral 144is an actuating shaft connected to the rack 143, the other end side ofwhich being fixed to the bottom part of the variable length blade part140. Reference numeral 145 is a bearing for supporting the actuatingshaft 144 by the blade body 102 for rotation.

With the 8^(th) embodiment, when the pinion 142 is rotated by thereversible motor 141 in the normal or reverse direction, the actuatingshaft 143 fixed to the rack 143 meshing with the pinion 142 is allowedto reciprocate in the direction of double arrows W. By the reciprocationof the actuating shaft 144, the variable length blade part 140 slides inthe longitudinal direction of the blade guided by the pair of slidebearings 148.

That is, when the actuating shaft 144 is moved upward by the rotation ofthe motor 141, the variable length blade part 140 moves radially outwardto be increased in tip diameter thereof.

When the actuating shaft 144 is pulled down by the rotation of the motor141 in the reverse direction, the variable length blade part 140 movesradially inward by stroke S to the position shown with chain line in thedrawing, resulting in a decreased tip diameter of the variable lengthblade part 140.

As described above, according to the 8^(th) embodiment, the activeannular plane area of the blade 100 is changeable by sliding thevariable length blade part 140 fit for sliding in the blade body 102.

Referring to FIG. 12 showing 9^(th) embodiment, a screw bar 161 having amale screw thread cut in the end portion is connected to the outputshaft 151 a of the motor 151, and said thread is engaged in a shaft withfemale screw thread 162 fixed to the bottom part of the variable lengthblade part 140.

With the 9^(th) embodiment, when the screw bar 161 is rotated by themotor 151, for example, in a clockwise direction, the shaft with femalescrew thread 162 and the variable length blade part 140 fixed theretomoves radially outward as shown with solid line in the drawing toincrease the tip diameter of the variable length blade part 140. Whenthe motor 151 is rotated in the reverse direction to rotate the screwbar 161 in a counterclockwise direction, the variable length blade part140 moves radially inward by stroke S to the position shown with chainline in the drawing resulting in a decreased tip diameter of thevariable length blade part 140.

The configuration other than described above is the same as the 8^(th)embodiment and components same as the 8^(th) embodiment are marked withthe same reference numerals.

In the 10^(th) embodiment shown in FIG. 13, a blade 100 is divided intwo to a blade body 102 fixed to said rotor 1103 and a variable lengthblade part 150 which define a part of blade from the middle to the tipof the blade 100.

The variable length blade part 150 is composed of a front core 156 madeof hard material such as a metal pipe, a rear core 158 made of wire ofsoft material, and a blade shell 157 made of flexible thin plate such ashigh strength cloth and defining a blade profile between the front core156 and rear core 158 as shown in FIG. 13(B), the front core 156 beingextended downward in the longitudinal direction of the blade to form anactuating shaft 154.

The actuating shaft 154 extending from the front core 156 is fit in abearing part 155 formed in the blade body 102 for sliding in thelongitudinal direction of the blade. Reference numeral 159 is a spaceformed in the blade body for accommodating the variable length bladepart 150.

Reference numeral 151 is a reversible motor, 152 is a pinion fixed to anend part of the output shaft 151 a of the motor 151. Reference numeral153 is a rack meshing with the pinion. Said actuating shaft 154 isconnected to the rack 153.

When changing the tip diameter of blade, the front core 156 of thevariable length blade part 150 is moved along the bearing part 155formed in the blade body 102 within the range of stroke S by therotation of the motor 151 via the pinion 152, rack 153, and actuatingshaft 154.

With the 10^(th) embodiment, blade profile of the variable length bladepart 150 is defined by the blade shell 157 of flexible material coveringbetween the front core 156 and rear core 158, so the variable lengthblade part 150 is light weighted and it can be folded parallel to thelongitudinal direction of the blade.

Referring to showing the configuration of the whole of the 11^(th)embodiment, reference numeral 1103 is a rotor having a plurality ofblades 100 (three blades in this example) attached on the peripherythereof at an equal spacing in the circumferential direction and havinga rotor shaft 1102 fixed to the rear end thereof. Said blades 100 areeach composed of a blade body part 102 fixed to said rotor 1103 and avariable length blade part 140 which is attached to said blade body part102 capable of being moved radially in the direction of blade length.Reference numeral 1101 is a support for supporting the wind turbine.

Reference numeral 201 is a blade stress detector for detecting stressesacting on said blade 100. It detects the maximum stress occurred in theblade 100 by means of a strain gage stuck on the position where themaximum stress occurs. Reference numeral 202 is a wind speed detectorfor detecting the speed of wind acting on the wind turbine. Referencenumeral 203 is a load detector for detecting the load of the windturbine such as generator load, which is the output of the wind turbine.

Reference numeral 204 is a rotation speed detector for detectingrotation speed of the rotating components of the wind turbine includingthe rotor 1103. The detected signals of said stress detector 201, windspeed detector 202, load detector 203, and rotation speed detector 204are inputted to a blade length control device 205.

Reference numeral 141 is a reversible motor, 207 is a motor controllerabout which is detailed later.

In FIG. 17 showing the construction of said blade 100, the blade 100 isdivided in two to a blade body 102 fixed to said rotor 1103 and avariable length blade part 140 which define a part of blade from themiddle to the tip of the blade 100.

Reference numeral 148 is a pair of slide bearing fixed to the blade body102. The sliding part 146 formed at the lower portion of the variablelength blade part 140 is fit to sliding surfaces of the pair of slidebearings 148 for sliding in the longitudinal direction of blade.

Reference numeral 141 is a reversible motor, 142 is a pinion fixed tothe end part of the output shaft 141 a of the motor 141. Referencenumeral 143 is rack meshing with said pinion 142. Reference numeral 144is an actuating shaft connected to the rack 143, the other end side ofwhich being fixed to the bottom part of the variable length blade part140. Reference numeral 145 is a bearing for supporting the actuatingshaft 144 by the blade body 102 for rotation.

Reference numeral 205 is a blade length control device the operation ofwhich is detailed later, 207 is a motor control device for controllingthe operation of the motor 141 receiving a control signal from the bladelength control device 205.

Next, the control operation of the wind turbine of the 11^(th)embodiment will be explained.

Referring to FIG. 15, reference numeral 205 is a blade length controldevice. The detected wind speed signal from the wind speed detector 202is inputted to a wind speed comparing section 255 of the blade lengthcontrol device 205, the detected rotation speed signal from the rotationspeed detector 204 is inputted to a rotation speed comparing section256, the detected load signal from the load detector 203 is inputted toa load comparing section 257, and the detected stress signal from theblade stress detector 203 is inputted to the stress comparing section258.

Reference numeral 251 is a permissible wind speed setting section wherethe permissible wind speed acting on the wind turbine, i.e., optimalwind speed, which is determined based on the stresses of the rotatingcomponents including the rotor 100 and the performance of the windturbine. Reference numeral 252 is a permissible rotation speed settingsection where the permissible rotation speed of the rotating componentsof the wind turbine, i.e., optimal rotation speed, which is determinedbased on the stresses of the rotating components including the rotor 100and the performance of the wind turbine. Reference numeral 253 is apermissible load setting section where the optimal load by thegenerator, etc. (optimal output of the wind turbine), which isdetermined based on the stresses of the rotating components includingthe rotor 100 and the performance of the wind turbine. Reference numeral254 is a permissible stress setting section where the maximumpermissible stress acting on the rotor 100 is set.

The wind speed comparing section 255 calculates the deviation of thedetected wind speed signal from the maximum value set beforehand in thepermissible wind speed setting section 251 and inputs the wind speeddeviation (result of comparison) to an optimal active annular plane areacalculating section 259. The rotation speed comparison section 256calculates the deviation of the detected rotation speed signal from theoptimal rotation speed set beforehand in the permissible rotation speedsetting section 252 and inputs the rotation speed deviation (result ofcomparison) to the optimal active annular plane area calculating section259. The load comparing section 257 calculates the deviation of thedetected load signal from the optimal load set beforehand in thepermissible load setting section 253 and inputs the load deviation(result of comparison) to the optimal active annular plane areacalculating section 259. The stress comparing section 258 calculates thedeviation of the detected stress signal from the permissible bladestress set beforehand in the permissible stress setting section 254 andinputs the blade stress deviation (result of comparison) to the optimalactive annular plane area calculating section 259.

The optimal active annular plane area calculating section 259 calculatesthe active annular plane area when one or a plurality of the deviationsare zero or near zero (Here, near zero means that the detected bladestress is smaller than the permissible blade stress by a small value.),in other words, calculates the active annular plane area to be adjustedto the area with which the wind turbine is operated under the optimaloperation condition concerning wind speed, rotation speed, or load. Theoptimal operation condition for example concerning rotation speed meansthat the wind turbine is operated with rotation speed at or near thepermissible rotation speed.

The optimal active annular plane area calculating section 259 calculatesthe active annular plane area when the blade stress deviation is zero ornear zero and at the same time any one or a plurality of the wind speeddeviation, rotation speed deviation, and load deviation, which aredeviations of operating conditions, are zero or near zero.

This means that the optimal active annular plane area calculatingsection 259 calculates the active annular plane area with which the windturbine is operated under optimal operating condition, i.e., with amaximum output power within permissible blade stress by monitoring andcontrolling the deviations of operating conditions and the deviation ofthe blade stress.

An optimal blade length calculating section 260 calculates the value ofthe length of the variable length blade part 140 to be adjustedcorresponding to the value of active annular plane area to be adjustedinputted from the optimal active annular plane area calculating section259.

A motor rotation angle calculating section 261 calculates the rotationangle of the motor to be rotated in order to adjust the length of bladeby the value inputted from the optimal blade length calculating section260.

Therefore, the blade length control device 205 decreases the length ofthe variable length blade part 140 to decrease the active annular planearea when detected wind speed is higher than the permissible wind speed,and to increases the length of the variable length blade part 140 toincrease the active annular plane area when detected wind speed is lowerthan the permissible wind speed.

The blade length control device 205 decreases the blade length todecrease the active annular plane area when the detected rotation speedis higher than the permissible rotation speed, and increases the bladelength to increase active annular plane area when the detected rotationspeed is lower than the permissible rotation speed.

The blade length control device 205 decreases the blade length todecrease the active annular plane area when the detected load is heavierthan the permissible load, and increases the blade length to increasethe active annular plane area when the detected load is lower than thepermissible load.

The blade length control device 205 decreases the blade length todecrease the active annular plane area when the detected blade stress ishigher than the permissible blade stress, and increases the blade lengthto increase the active annular plane area when the detected stress islower than the permissible load, in addition to controlling the bladelength in correspondence to wind speed, rotation speed, and load.

The rotation angle signal for rotating the reversible motor 141calculated in the motor rotation angle calculating section 261 isinputted to the motor control device 207, which allows the motor 141 torotate by an angle corresponding to said rotation angle signal.

As shown in FIG. 17, which shows an example of adjusting blade length inthe case of the embodiment of FIG. 11, when the pinion 142 is rotated inthe normal or reverse direction by the reversible motor 141, the rack143 meshing with the pinion 142 and the actuating shaft 144 fixed to therack 143 reciprocates in the direction of double arrow W. By thereciprocating movement of the actuating shaft 144, the variable lengthblade part 140 fixed to the actuating shaft 144 slides in the in thelongitudinal direction of blade with the sliding portion 146 guidedalong the slide bearing 148.

That is, when the actuating shaft 144 is moved upward by the rotation ofthe motor 141, the variable length blade part 140 moves radially outwardto be increased in tip diameter thereof.

When the actuating shaft 144 is pulled down by the rotation of the motor141 in the reverse direction, the variable length blade part 140 movesradially inward by stroke S to the position shown with chain line in thedrawing, resulting in a decreased tip diameter of the variable lengthblade part 140.

Therefore, according to the embodiment, the active annular plane area ofthe blade 100 can be varied by sliding the variable length blade part140 fit in the blade body 102 for sliding upward or downward in FIG. 17.

As described above, according to the 11^(th) embodiment, the output ofthe wind turbine can be maintained always in the maximum output level bycontrolling the active annular plane area so that the area is optimal incorrespondence to the operating conditions of the wind turbine such aswind speed, rotation speed and load of the wind turbine by means ofoperation control through the blade length control device 205.

Further, as it becomes possible to control the length of variable lengthblade part 140 so that the active annular plane area is optimal for boththe permissible values of wind speed, rotation speed and load of thewind turbine and the permissible value of blade stress, the occurrenceof excessive stress in the rotating components of the wind turbine dueto rapid increase of wind speed and load, etc., is avoided and fatiguefailure of the rotating elements can be prevented.

Therefore, the wind turbine can be operated while always automaticallycontrolling the length of the variable length blade part 140 so that theoccurrence of fatigue failure of the rotating components, such as theblades 100 and rotor 1103, and at the same time the wind turbine isoperated with the optimal active annular plane area which ensures amaximum output of the wind turbine while avoiding the fatigue failure.Accordingly, the operation of the wind turbine is possible with anoptimal maximum output with an extended fatigue life of the rotatingelements such as the blades and rotor.

Referring to FIG. 18˜20 showing the 12^(th) embodiment, referencenumeral 1101 is a support, 304 is a nacelle supported on said support1101 via a well known yaw control device (not shown is the drawing) forrotation around the axis of rotation 350 a of the nacelle 304, anelectric generator 307 being accommodated in the nacelle 304. Referencenumeral 1102 is a turbine shaft connecting a rotor head 350 to thegenerator 307, 309 is a bearing for supporting the turbine shaft 1102 bythe nacelle 304.

A plurality of connecting elbows (three of elbows in this example) isattached to said rotor head 350 at an equal spacing in thecircumferential direction by the means described later, and a blade isattached to each of the connecting elbows 301.

Although the wind turbine is configured in a downwind type with therotor head 350 and blades 100 positioned down the wind from the axis ofrotation 1105 a of the nacelle, it is suitable to configure the windturbine in an upwind type with the rotor head 350 and blades 100positioned toward the wind from the axis of rotation 1105 a of thenacelle.

Reference numeral 300 is a blade tilting mechanism as described below.

Reference numeral 301 is a connecting elbow, a hollow tube (it may be asolid body) bent by an angle β in the plane perpendicular to the axis ofrotation 350 a of the rotor head 350 into L like shape. Said angle β issuitable to be 90°, however, it may be an obtuse angle between 90° andabout 120°.

Referring to FIG. 20 showing the structure of attaching part of theconnecting elbow 301 for attaching to the rotor head 350, referencenumeral 302 is an external ring gear fixed to the lower part of theconnecting elbow 301 concentric with the axis of rotation 301 a thereof.Reference numeral 303 is a pinion fixed to the end part of the outputshaft 304 a of a driving motor 304 and meshes with the ring gear 302.

Reference numeral 305 is a bearing attached between the inner peripheryof the ring gear 302 and the outer periphery of the rotor head 350. Anend of the connecting elbow 301 is fixed to the ring gear 302, and theyare rotatable about the center axis of 300 a of the rotor head 350 viathe bearing 305.

The blade 100 is attached to the other end of the elbow 301 for rotationas described below.

Referring to FIG. 21 showing the detail of a pitch angle controllingdevice 330, reference numeral 333 is an external ring gear fixed to thelower end of the blade 100, 334 is a bearing attached between the innerperiphery of the ring gear 333 and the other end of the connecting elbow301. The blade 100 is rotatable relative to the connecting elbow 301 viathe bearing 334 to adjust blade pitch angle to a desired angle.

Reference numeral 331 is a pitch angle control motor fixed to theconnecting elbow near the periphery of the other end thereof by means ofa bracket 335. Reference numeral 332 is a pinion fixed to the outputshaft of the pitch angle control motor 331 and meshes with the externalring gear 333.

Therefore, in the pitch angle control device 330, the ring gear 333 isrotated by the pitch angle control motor 331 via the pinion 332 and theblade 100 fixed to the ring gear 333 can be fixed in the desired pitchangle position.

With this construction, maintainability of the pitch angle controldevice 330 is enhanced as the ring gear 333 is of a external gear.

Returning to FIG. 20, reference numeral 306 is a motor control devicefor controlling the driving motor 304, 321 is a wind speed detector fordetecting the wind speed acting on the blades 100, and 360 is acontroller which calculates the tilt angle of the connecting elbow,i.e., the tilt angle of the blade 100 based on the detected wind speedfrom the wind speed detector 321 and output the result to the motorcontrol device 306.

When operating the wind turbine of the 12^(th) embodiment, the detectedwind signal of the wind speed acting on the blade is inputted to aaverage wind speed calculating section 361 of the controller 360 asshown in FIG. 22.

The average wind speed calculating section 361 calculates average windspeed V during a determined time period and input it to a wind turbineoutput calculating section 363. Reference numeral 362 is a windspeed/output setting section where is set a lower limit average windspeed V₂ and a higher limit wind speed V₁. When average speed V is lowerthan V₂ the tilt angle of the blade 100 (see FIG. 19) is kept to zero,that is the blade tilt position of maximum active annular plane area,when average wind speed V is higher than V₁, limit speed of higher side,the tilt angle α of the blade 100 is kept to the minimum angle to reducethe active annular plane area to a minimum.

In a wind turbine output power calculating section 363 is set therelations between average wind speed V and wind turbine output P asshown in FIG. 22(B). Each of the curves a, c, and b shows the relationbetween wind speed and the output of wind turbine with constant activeannular plane area.

When average wind speed V is medium between V₂ and V₁, the output P atthe intersection of the curve c in FIG. 22(B) and the vertical line ofthe average wind speed which is between V₂ and V₁ is selected(calculated) in the wind turbine output power calculating section 363and said selected (calculated) power P is inputted to an active annularplane area calculating section 364.

The active annular plane area calculating section 364 calculates theactive annular plane area S corresponding to said selected (calculated)wind turbine output P and inputs the result to a blade diametercalculating section 365. The blade diameter calculating section 365calculates the blade tip diameter corresponding to said calculatedactive annular plane area S and output the result to a blade tiltangle/connecting elbow rotation angle calculating section 366.

The blade tilt angle/connecting elbow rotation angle calculating section366 calculates the required tilt angle for realizing said calculatedblade tip diameter and further calculates the required rotation angle ofthe connecting elbow 301 for realizing the rotation of the blade to theposition of said tilt angle α, and inputs the calculated rotationalangle of the connecting elbow 301 to the motor control device 306.

The motor control device 306 allows the drive motor 304 to be rotated torotate the connecting elbow 301 to the position of said calculated angleα and to be kept in the position.

In FIG. 22(B), only a single curve c is set for average wind velocity Vbetween the lower limit wind speed V₂ and higher limit wind speed V₁, aplurality of curves may be set for a plurality of average wind speedranges between V₂ and V₁.

As described above, according to the 12^(th) embodiment, when averagewind speed V is lower than a predetermined lower limit of average windspeed V₂, the active annular plane area is increased to the maximum byerecting the blades 100 to the vertical position as shown with solidline in FIG. 19 to get the most out of the wind energy. In this case, aswind speed is low, fatigue failure does not occur in the rotatingcomponents such as the blades 100 and rotor head 350 by increasing theactive annular plane area to increase the amount of wind energy of windtaken in to the wind turbine.

When the average wind speed V is higher than predetermined higher limitof average wind speed V₁, the tilt angle α of the blades 100 isincreased as shown with chain line in FIG. 19 to decrease the activeannular plane area to avoid the occurrence of fatigue failure in therotating components.

Further, when wind speed is between V₂ and V₁, the energy of windtaken-in to the wind turbine is adjusted by changing the tilt angle α ofthe blades 100 according to curve c in FIG. 22(B), where curve c may bea plurality of curves corresponding to a plurality of average speedranges between V₂ and V₁ as mentioned above, and the wind turbine isoperated under optimal operating condition taking into considerationfatigue failure in the rotating components.

By this, the operation of the wind turbine is possible with the bladesset to the position of tilt angle α corresponding to an active annularplane area with which the output of the wind turbine is a maximum withinthe range of evading the occurrence of fatigue failure in the rotatingcomponents such as the blades 100 and rotor head 350.

Further, by changing the distance C in FIG. 20, that is the distancefrom the axis of rotation of the connecting elbow 301 to the end facefor attaching the blade 100, the tip diameter of the blade can bechanged. Therefore, by preparing connecting elbows of different lengthC, active annular plane area can be changed only by changing theconnecting elbow 301 without preparing blades of different blade length.

FIG. 23 illustrates schematically the side view of wind turbine of the13^(th), 14^(th), and 15^(th) embodiment. In the drawing, a plurality ofblades 100 are attached to a rotor head 350 by means of the mechanismdescribed later. Reference numeral 1101 is a support on the top of whicha nacelle 304 is mounted by means of a yaw control device 4106 which iswell known. In the nacelle 304 is accommodated an electric generator307. Reference numeral 1102 is a turbine shaft for connecting the rotorhead 350 to the generator 307, 309 is a bearing for supporting theturbine shaft 1102 by the nacelle 304.

Although the wind turbine is configured in a downwind type with therotor head 350 and blades 100 positioned down the wind from the axis ofrotation 1105 a of the nacelle, it is suitable to configure the windturbine in an upwind type with the rotor head 350 and blades 100positioned toward the wind from the axis of rotation 1105 a of thenacelle.

Referring to FIG. 23, 24 showing the 13^(th) embodiment, referencenumeral 100 represents the blades attached to the rotor head 350 by themeans described below, three blades being attached as shown in FIG. 24(a plurality of blades other than three may be suitable).

Reference numeral 400 is a blade tilting mechanism composed as follows.

Reference numeral 4103 is a blade link, an end of which is attached tothe blade 100 via a pitch angle control device 4102. The blade link 4103is supported at its middle part by the forked supporting part 451 formedat an end part of the rotor head 350 via a supporting shaft 406 forswinging.

Reference numeral 401 is a hydraulic actuator fixed to the rotor head350, the output rod 402 of the actuator being movable in the directionof the axis of rotation 350 a of the rotor head 350. Reference numeral403 is a blade link guide having protruded portions in each of which agroove is defined for receiving each of rollers 405 which is fit forrotation to each of pins 404 fixed to the other end part of each of theblade links 4103.

With this construction, each blade link 4103, accordingly each blade 100is swung around the supporting shaft 406 via the blade link guide 403and roller 404 when the output rod 402 of the hydraulic actuator 401moves in the direction of the axis of rotation of the rotor head 350.

Reference numeral 421 is a wind speed detector for detecting the windspeed acting on the blades 100, 460 is a controller which calculates thetilt angle θ of the blade 100 based on the detected wind speed from thewind speed detector 421 and outputs the result to an actuator controldevice 420 which drives the hydraulic actuator 401 on receiving thecontrol signal from the controller 460, and 422 is a hydraulic source ofthe hydraulic actuator 401.

In the operation of the wing turbine of the 13^(th) embodiment, as shownin FIG. 28, the detected signal of the wind speed acting on the blades100 detected by the wind speed detector 421 is inputted to an averagewind speed calculating section 461, which calculates the average windspeed V during a determined time period and inputs the result to a windturbine output calculating section 463.

Reference numeral 462 is a wind speed/output setting section where isset a lower limit average wind speed V₂ and a higher limit wind speedV₁. When average speed V is lower than V₂ the tilt angle θ of the blade100 (see FIGS. 23, 25, 26) is kept to 180°, that is the blade tiltposition of a maximum active annular plane area, when average wind speedV is higher than V₁, limit speed of higher side, the tilt angle θ of theblade 100 is kept to the minimum angle to reduce the active annularplane area to the minimum.

In a wind turbine output power calculating section 463 is set therelations between average wind speed V and wind turbine output P asshown in FIG. 28(B). Each of the curves a, c, and b shows the relationbetween wind speed and the output of wind turbine with constant activeannular plane area.

When average wind speed V is medium between V₂ and V, the output P atthe intersection of the curve c in FIG. 22(B) and the vertical line ofthe average wind speed which is between V₂ and V, is selected(calculated) in the wind turbine output power calculating section 463and said selected (calculated) power P is inputted to an active annularplane area calculating section 464.

The active annular plane area calculating section 464 calculates theactive annular plane area S corresponding to said selected (calculated)wind turbine output P and inputs the result to a blade diametercalculating section 465. The blade diameter calculating section 465calculates the blade tip diameter corresponding to said calculatedactive annular plane area S and output the result to a blade tiltangle/connecting elbow rotation angle calculating section 466.

The blade tilt angle calculating section 466 calculates the requiredtilt angle θ for realizing said calculated blade tip diameter and outputthe result to an actuator control device 420, which controls thesupply/exhaust of the working fluid to or from the actuator 401 to movethe output rod 402 so that the blades 100 are tilted by an angle θcalculated based on the average wind speed V and allows the blade to bekept in the position of the angle θ.

In FIG. 28(B), only a single curve c is set for average wind velocity Vbetween the lower limit wind speed V₂ and higher limit wind speed V₁, aplurality of curves may be set for a plurality of average wind speedranges between V₂ and V₁.

As described above, according to the 13^(th) embodiment, when averagewind speed V is lower than a predetermined lower limit wind speed V₂,the active annular plane area is increased to the maximum by erectingthe blades 100 to the vertical position (θ=180°) as shown with chainline in FIG. 23 to get the most out of the wind energy. In this case, aswind speed is low, fatigue failure does not occur in the rotatingcomponents such as the blades 100 and rotor head 350 by increasing theactive annular plane area to increase the energy of wind taken in to thewind turbine.

When the average wind speed V is higher than higher limit wind speed V₁,the tilt angle θ of the blades 100 is decreased, as shown with a solidline in FIG. 23, to decrease the active annular plane area to avoid theoccurrence of fatigue failure in the rotating components.

Further, when wind speed is medium between V₂ and V₁, the energy of windtaken-in to the wind turbine is adjusted by changing the tilt angle θ ofthe blades 100 according to curve c in FIG. 22(B), where curve c may bea plurality of curves corresponding to a plurality of average speedranges between V₂ and V₁ as mentioned above, and the wind turbine isoperated under optimal operating condition taking into considerationfatigue failure in the rotating components.

By this, the operation of the wind turbine is possible with the bladesset to the position of tilt angle θ corresponding to an active annularplane area with which the output of the wind turbine is maximum withinthe range of evading the occurrence of fatigue failure in the rotatingcomponents such as the blades 100 and rotor head 350.

Referring to FIG. 25 showing the 14^(th) embodiment, the blade tiltingmechanism, which is a modification of the blade tilting mechanism ofFIG. 23, 24, is composed as follows. In the drawing, the same part asthat of FIG. 23, 24 is marked with the same reference numeral.

Reference numeral 410 is a servomotor fixed to the rotor head 350, theoutput shaft 411 of the servomotor 410 has a male screw thread part 412with which the female screw thread of a blade link guide 413 is engaged.The blade link guide 413 has protruded portions in each of which agroove is defined for receiving each of rollers 405 which is fit forrotation to each of pins 404 fixed to the other end part of each of theblade links 4103. The construction other than mentioned above is thesame as that of FIG. 23, 24 of the 13^(th) embodiment.

With this construction, the blade tilt angle θ can be changed by thereciprocation of the blade link guide 413 by the rotation of the outputshaft 411 of the servomotor 410 rotating the servomotor 410.

Referring to FIG. 15 of the 15^(th) embodiment, the blade tiltingmechanism is composed as follows.

Two blade links 4103 to each of which is fixed the blade 100 areattached for swinging to the rotor head 350 via supporting shafts 432 atthe front end near the periphery of the rotor head 350. Referencenumeral 435 is a bracket fixed to the rotor head at the front endthereof. A hydraulic cylinder 430 is attached supported via a hydrauliccylinder supporting shaft 434 and a pin 433 between the end part of thebracket 435 and the middle part of each of the blade links 4103.

The tilt angle, or spread angle θ, of the blades 100 can be changed bythe movement of the rod 431 of the hydraulic cylinder 430. Theconstruction other than mentioned above is the same as that of FIG. 23,24 of the 13^(th) embodiment, and the same as that of FIG. 23, 24 ismarked with the same reference numeral.

With the 15^(th) embodiment, the active annular plane area is changeableby changing the spread angle θ of the blades to adjust active annularplane area so that the wind turbine is operated under the optimalcondition taking fatigue failure in the rotating components intoconsideration.

As has been described in the foregoing, according to the presentinvention, the blades are moved in radially outward directions toincrease the active annular plane area as detected wind speed decreases,and the blades are moved in radially inward directions to decreaseactive annular plane area as detected wind speed increases. Bycontrolling the radial position of the blades like this, the windturbine can be operated so that the output as high as possible isobtained while evading the occurrence of fatigue failure of the rotatingcomponents such as the blades and r otor under the present wind speed.

Therefore, the wind turbine can be operated while always automaticallycontrolling blade length so that the occurrence of fatigue failure ofthe rotating components such as the blades and rotor, and at the sametime the wind turbine is operated with the optimal active annular planearea which ensures the maximum output of the wind turbine within therange capable of evading the fatigue failure. Accordingly, the operationof the wind turbine is possible with an optimal maximum output withelongated fatigue life of the rotating elements such as the blades androtor.

According to the present invention, the active annular plane area can beadjusted to an optimal area in correspondence with wind conditions evenin the operation of the wind turbine by changing the effective bladelength through changing tip diameter of blades by moving the blades inthe radial direction of the rotor via the blade length varyingmechanism.

By this adjustment, the operation of the wind turbine can be performedso that the output is the maximum within the condition capable ofevading the occurrence of fatigue failure of the rotating componentssuch as the blades and rotor.

Therefore, the wind turbine can be operated while always automaticallycontrolling blade length so that the occurrence of fatigue failure ofthe rotating components such as the blades and rotor, and at the sametime the wind turbine is operated with the optimal active annular planearea which ensures the maximum output of the wind turbine within therange capable of evading the fatigue failure. Accordingly, the operationof the wind turbine is possible with an optimal maximum output withelongated fatigue life of the rotating elements such as the blades androtor.

Further, the blade length varying mechanism is constructed light inweight and can be provided inside the blade, so the active annular planearea is variable without accompanying the increase in the weight ofblade.

Further, according to the present invention, the active annular planearea can be controlled so that the wind turbine is always operated withan optimal output level by controlling the active annular plane area sothat the area is optimal for the wind turbine operating conditions suchas wind speed, rotation speed and load of the wind turbine through theblade length control device. Therefore, the action of an excessivelyhigh stress on the rotating components of the wind turbine due to arapid increase in wind speed or load is suppressed resulting in theprevention of fatigue failure of the rotating components.

Therefore, the wind turbine can be operated while always automaticallycontrolling blade length so that the occurrence of fatigue failure ofthe rotating components such as the blades and rotor and at the sametime with the optimal active annular plane area which insures a maximumof the wind turbine output within the range capable of evading thefatigue failure. Accordingly, the operation of wind turbine is possiblewith an optimal maximum output with elongated fatigue life of therotating elements such as the blades and rotor.

Further, according to the present invention, the problem that may occurwith conventional wind turbines having no adjusting means for theadjusting active annular plane area, i.e., the occurrence of fatiguefailure of the rotating components such as the blade and rotor due toexcessive high speed wind sometimes experienced by a gust of wind isprevented, and the wind turbine can be operated with a maximum outputwithin the range of evading the occurrence of fatigue failure of therotating components such as the blades and rotor by tilting the bladesthrough changing the rotation angle of each connecting elbow accordingto the speed of the wind acting on the blades.

Therefore, the wind turbine can be operated while always automaticallycontrolling blade length so that the occurrence of fatigue failure ofthe rotating components such as the blades and rotor and at the sametime with the optimal active annular plane area which insures a maximumof the wind turbine output while avoiding the fatigue failure.Accordingly, the operation of wind turbine is possible with an optimalmaximum output with elongated fatigue life of the rotating elements suchas the blades and rotor. Thus, the problem of fatigue failure due toexcess wind speed of a gust of wind is prevented.

Further, by changing the distance from the axis of rotation of theconnecting elbow to the end face thereof for attaching the blade, thetip diameter of the blade can be changed, so that active annular planearea can be changed by preparing several connecting elbows different insaid distance and only changing the connecting elbow without preparingblades of different blade length.

Further, according to the present invention, by adjusting the activeannular plane area through changing the tilt angle of blade respondingto the detected speed of the wind acting on the blades, the wind turbineis operated with an optimal maximum output within the range of evadingthe occurrence of fatigue failure in the components such as blades androtor.

Therefore, the wind turbine can be operated while always automaticallycontrolling blade length so that the occurrence of fatigue failure ofthe rotating components such as the blades and rotor and at the sametime with the optimal active annular plane area which insures a maximumof the wind turbine output while avoiding the fatigue failure.Accordingly, the operation of wind turbine is possible with an optimalmaximum output with elongated fatigue life of the rotating elements suchas the blades and rotor.

1. A wind turbine with an active annular plane area control mechanismcomprising a plurality of blades attached to a rotor for transmittingthe wind force acting on the blades to the output shaft of the windturbine connected to the rotor, wherein said rotor is formed in acylindrical shape, said blades are attached to said rotor movable in theradial direction of the rotor, a blade shifting mechanism is connectedto the roots of said blades for reciprocating said blades in the radialdirection, and an active annular plane area is changeable by moving saidblades in the radial direction through said blade shifting mechanism,wherein said rotor has radial fit holes located at an equal spacing inthe circumferential direction, said blades are received in said radialfit holes for reciprocation, and said blade shifting mechanism isprovided in the hollow of said rotor, and wherein said blade shiftingmechanism comprises a plurality of screw bars received for rotation inradial holes provided in the cylindrical wall of said rotor, sleeveseach of which is engaged with each of the screw bars, links each ofwhich connects each of said sleeves and said blades, pinions each ofwhich is fixed to each of said screw bars at the inner side partthereof, and a driving gear meshing with said pinions and driven by adriving device; and said blades are reciprocated in the radial directionthrough the expansion or contraction of said links resulting from theshifting of said sleeves by the rotation of said screw bars when saiddriving gear is rotated by said driving device.
 2. A wind turbine withan active annular plane area control mechanism, comprising a pluralityof blades attached to a rotor for transmitting the wind force acting onthe blades to the output shaft of the wind turbine connected to therotor, wherein said rotor is formed in a cylindrical shape, said bladesare attached to said rotor movable in the radial direction of the rotor,a blade shifting mechanism is connected to the roots of said blades forreciprocating said blades in the radial direction, and an active annularplane area is changeable by moving said blades in the radial directionthrough said blade shifting mechanism, wherein said rotor has radial fitholes located at an equal spacing in the circumferential direction, saidblades are received in said radial fit holes for reciprocation, and saidblade shifting mechanism is provided in the hollow of said rotor, andwherein said blade shifting mechanism comprises a supporting elementlocated in the center part of said rotor; pairs of links capable ofbeing expanded or contracted, each pair connecting the root of eachblade to said supporting element, screw bars each connecting one side ofeach of said pairs of links, and driving devices for rotating said screwbars; and the radial position of said blades is changeable by expandingor contracting said pairs of links through rotating said screw bars bysaid driving devices.
 3. A wind turbine with an active annular planearea control mechanism, comprising a plurality of blades attached to arotor for transmitting the wind force acting on the blades to the outputshaft of the wind turbine connected to the rotor, wherein said rotor isformed in a cylindrical shape, said blades are attached to said rotormovable in the radial direction of the rotor, a blade shifting mechanismis connected to the roots of said blades for reciprocating said bladesin the radial direction, and an active annular plane area is changeableby moving said blades in the radial direction through said bladeshifting mechanism, wherein said rotor has radial fit holes located atan equal spacing in the circumferential direction, said blades arereceived in said radial fit holes for reciprocation, and said bladeshifting mechanism is provided in the hollow of said rotor, and whereinsaid blade shifting mechanism comprises two rings, an outer ring and aninner ring, provided concentric with the center axis of said rotorrotatable in the direction contrary to each other, pairs of linkscapable of being expanded or contracted, each pair connecting the rootof each blade to the outer ring with one of the pair and to the innerring with the other of the pair, a driving device for rotating said tworings in the direction contrary to each other, and a supporting elementlocated in the center part of said rotor and supports one of said rings;and said blades can be reciprocated in the radial direction by expandingor contracting said pairs of links through rotating said rings in thedirection contrary to each other.
 4. A wind turbine with an activeannular plane area control mechanism, comprising a plurality of bladesattached to a rotor for transmitting the wind force acting on the bladesto the output shaft of the wind turbine connected to the rotor, whereinsaid rotor is formed in a cylindrical shape, said blades are attached tosaid rotor movable in the radial direction of the rotor, a bladeshifting mechanism is connected to the roots of said blades forreciprocating said blades in the radial direction, and an active annularplane area is changeable by moving said blades in the radial directionthrough said blade shifting mechanism, wherein said rotor has radial fitholes located at an equal spacing in the circumferential direction, saidblades are received in said radial fit holes for reciprocation, and saidblade shifting mechanism is provided in the hollow of said rotor, andwherein said blade shifting mechanism comprises a slider received in aslider receiver fixed to the rotor for sliding in the radial directionof the rotor, the slider having a screw thread hole directed in theradial direction, links each of which has a curved convex surface at anend thereof to be engaged in a convex of curved surface formed in saidslider receiver to be supported for swinging, the other end having anelongated hole through which the link is connected to the lower end partof the blade via a pin fixed to said lower end part, a screw bar engagedwith said screw thread hole of said slider, and a driving device forrotating said screw bar; and the blades can be reciprocated in theradial direction via said elongated hole and said pin engaging in saidhole by moving said slider in the radial direction in said sliderreceiver through rotating said screw bar by the rotation of said drivingdevice.